The present invention relates to flowmeters for measuring the mass per unit time of flow of a liquid. More particularly, the present invention is a flowmeter for measuring a quantized mass of fuel flow. Still more particularly, the present invention is a flowmeter of the aforesaid type capable of measuring extremely small fuel mass flow quanta.
The ever increasing sophistication of control of the various processes of internal combustion engines has provided increased mileage, decreased emissions and better overall performance. These advances include the widespread use of electronic controls and fuel injection. Fuel injectors, controlled electronically, provide precise, timed fuel injections directly into the combustion chamber at the most opportune portion of the engine cycle. One of the remaining issues of engine control relates to knowing the real-time quantized fuel flow mass delivered to a combustion chamber by its respective fuel injector.
Fuel flows, on a cycle resolved or on a per injection basis, have been difficult, if not impossible to quantify using conventional mass flowmeters. Therefore, a new style of mass flow meter is required to quantify small flows (mass quanta) accurately to within 0.1 mg per injection. The need for this type of higher accuracy device is to make better mass specific emission measurements. Fast low flow exhaust devices exist for cycle resolved missions but no information is available for cycle resolved input of the reactants. Further, most other flowmeters do not operate at the high pressures required for direct injection internal combustion engines.
Accordingly what remains needed in the art is a flowmeter capable of measuring extremely small fuel mass flow quanta in real-time.
The present invention is a flowmeter capable of real-time fuel ass flow measurement involving extremely low fuel mass flow quanta.
The flowmeter according to the present invention includes a dual flow path conduit system, a flow control for alternating the selection of one flow path exclusive of the other flow path, an indicator tube interfaced with the conduit system, an indicator shuttle slidably mounted in the indicator tube, and a sensor for sensing the position of the indicator shuttle relative thereto.
In operation, one flow path is first selected, whereupon a first quantum of fuel mass flows down the first selected flow path, causing the indicator shuttle to be displaced in a first direction along the indicator tube an amount related to the volume of the first quantum of fuel mass flow. This first displacement is registered by the sensor, for example optically via change in area of indicator shuttle occlusion of a photo-sensor with respect to a laser source, and is then output to an electronic circuit. Next, the other path is secondly selected, whereupon a second quantum of fuel mass flows down the second selected flow path, causing the indicator shuttle to be displaced in a second direction (opposite to the first direction) along the indicator tube an amount related to the volume of the second quantum of fuel mass flow. This second displacement is also registered by the sensor, again for example optically via change in area of indicator shuttle occlusion of a photo-sensor with respect to a laser source, and is then output to the electronic circuit. A simple algorithm of the electronic circuit calculates the fuel mass flow of each sensor output. This real-time generated fuel mass flow data is then, for example, used by the engine control module to adjust engine operational parameters pursuant to programming.
Accordingly, it is an object of the present invention to provide a flowmeter having the capability of measuring in real-time extremely low fuel mass flow quanta.